So it's finally here. After discussing it quite a lot and getting so many ideas (thank you Sailor, Linuxboy, FarmerJD) on the thread 'Need a reliable thermometer' here: http://cheeseforum.org/forum/index.php/topic,5523.30/topicseen.html I finally put it together this afternoon with a little help from my friends. My friends Lisa and Abe from Sous Vide blog http://qandabe.com/ dropped by with tools and before I knew it, this thing was up and running.

When I began thinking about a sous vide machine that would not cost $400-$5000, I immediately began to understand the enormous potential it has to make a perfect cheese vat. At first, I did sous vide in the cheese vat and that's where I met Lisa and Abe who inspired me to get a proper digital apparatus of controller and heater in there on the cheap and accurate. I then embarked on finding a form factor that can combine both uses: cheesemaking and sous vide.

Sous what?Sous vide (French for "under vacuum") for those who are not familiar, is a popular and miraculous cooking techniques where stuff gets cooked in vacuum bags in tepid water that are tuned up to a specific target point. Food pasteurizes and then cooks 100% evenly. It can never, ever get overcooked or burned. In fact, it keeps its colors, vitamins and minerals. Moreover, because of the vacuum, 100% of the moisture is kept in. A steak can remain in sous vide for 2 hours or 8 hours; doesn't matter, it will always be perfect medium as long as the water are at 140F. You often see this technique being used by top chefs and in shows like Iron Chef. This machine does what their $5000 immersion circulators do - perfectly. It fits cheesemaking because of its form factor (low and wide - great to cut curd) and its deadly accuracy in low temperatures. Its double boiler configuration prevents milk scalding too!

So what do we need?A pot, double boiler cooking vessel if possible. Heating element. A pump to circulate and even the water temp out around by blowing some air into it (Used in sous vide only - not in cheesemaking), an industrial-grade thermocouple (digital thermometer probe), a PID controller to take temp measurements from the thermocouple and decide based on our settings at what temperature to turn on/off the heating element. We also need a solid state relay to take these commands from the PID controller and do the actual high voltage switching. It is also important that ALL wires and terminals used for these connections, (no exception!), are high-temp insulated and properly rated to at least 25A. Any other wire WILL BURN under the heat of the 1350W element - guaranteed! That's about it for the shopping list.

Choosing a VesselI wasn't a fan of immersion heaters in a pot as they would scald the milk. The solution would have been to buy an inner pot to serve as a double boiler but think of the cost and the bulkiness. Immersion heaters and bucket heaters are also notoriously weak and unreliable. After investigating several form factors and vessels, from restaurant food tubs to converting a deep fryer, I had my eureka moment in a suburban department store's after-holiday clearance. An electric turkey roaster! Suddenly the lamest of the suburban white elephants had become the hottest concept since sliced cheese! First of, these things are huge! (18-22 quarts for my small batches is more than plenty). Secondly, it has a removable cookwell that sits inside the heated mother cookwell - say what? Yes! A built-in double boiler! No milk scalding! Third, rather than heating elements on the bottom or submerged elements like immersion heater or like in electric kettles, roasters feature a single continuous heating element that is wrapped like a belt all around the cooking well. The heat comes quickly and evenly from all the sides at once instead of taking its leisurely time from a single spot or the bottom. That means less mixing needed and much faster heating time of the milk (which reduces the pathogen and any bacterial growth during heating and pre-acidification. Fantastic!). The forth reason was the shallow pan instead of a tall pot - this will allow me to easily cut curd horizontally - something I always find impossible with a pot. Just like a big commercial vat. Fifth, the flimsy traditional design and crude construction meant that two screws are all that hold this thing together. Easy to take apart and put together again after surgery. Lastly, at $40; I couldn't resist. Here's the "before" shot...

Getting it doneTaking apart the cover was easy with 2 screws. There is a big nothing inside. (PIC 1) Lots of fiber glass insulation, high temp wires with porcelain terminals. One connected directly to one end of the heating element. The other, connects to the thermostat which is then connected to the other end of the heating element. We removed the fiber glass insulation with gloves so that we can perform the "surgery" without getting pricked by that nasty insulation. We then disconnected the wires from their terminals, removed the (very stubborn) thermostat. Passed the wires through the hole where the thermostat used to be. Connected the solid state relay on the appliance's exterior and then connected the PID to it (PIC 2).Then, it was time to connect the thermocouple to the PID. Having external thermocouple was the best option if I want to use this for cheese too because mounting a permanent thermocouple inside the vessel would be in the way of stirring and curd cutting . It was then time to put back the fiberglass insulation (PIC 3) and close the cover.For testing purposes, we did not mount the PID and relay in a nice sturdy screwed-on stainless housing quite yet... (will do that next week and post photos here). For now we just taped it to the side of the appliance. (PIC 4)Filled up with water, we were now ready to test it. Now Abe was ready to do his magic and he programmed the PID to detect the thermocouple and switch the heating element on/off (PIC 5)We now used a cheap-o aquarium air pump to bubble it up by placing its silicone hose in the water (I may integrate this into the appliance in the future with on/off switch as it must remain off during cheesemaking - but for now it's an optional external accessory). I wrapped the thermocouple to prevent water from going in (will permanently seal it with silicone later this week). and ...voila! Digital Sous vide machine and cheese vat - Done! (PIC 6) In that last photo it is tuned up to hold temp at 80C and is indicating it is still climbing and is currently at 35.4C. We did metric Celsius system instead of the Fahrenheit

Wow! All I can say is wow. Looks like a fantastic solution. If I studies this for a day I may be able to figure it all out. I'm jealous of all you men with your mechanical solutions (also just read about Farmer's motorizer stir solution). Thank for you sharing in such detail. I need that!Susan

I now want to pick your brain as to more specifics. I have the very same unit and just recently used it as is for making a Stilton and an Asiago. It performed well as is, but it had to be watched constantly and the manual aspect of temperature changes was difficult. Each are 27 days old, so a complete verdict is not yet possible, I will pass judgement in about a month.

First, when you heat and cook do you use the inner pan? If so you don't put liquid between the inner and out shell do you? The way I used it was to set then inner shell pan into the unit and I believe it is a slip fit with very little room between the wall.

I did experience a little scalding but not bad. I think this would be eliminated with your PID.

Second, can you give us a parts list of the PID and solid state relay that you used.

Logged

Cheese and Salumi: Cheese is Salumi from Milk, Salumi is Cheese from Meat. You bring the wine, I'll bring Cheese and Salumi!

I now want to pick your brain as to more specifics. I have the very same unit and just recently used it as is for making a Stilton and an Asiago. It performed well as is, but it had to be watched constantly and the manual aspect of temperature changes was difficult. Each are 27 days old, so a complete verdict is not yet possible, I will pass judgement in about a month.

First, when you heat and cook do you use the inner pan? If so you don't put liquid between the inner and out shell do you? The way I used it was to set then inner shell pan into the unit and I believe it is a slip fit with very little room between the wall.

I did experience a little scalding but not bad. I think this would be eliminated with your PID.

Second, can you give us a parts list of the PID and solid state relay that you used.

I'll admit my engineering ineptitude when I had wondered how the thermocouple worked; I presume it's used to measure the water jacket temp and given that it is an external probe, don't know how it drives the PID scheme; and yes, the actual components used would be very greatly appreciated. But the idea itself is already much appreciated.

I now want to pick your brain as to more specifics. I have the very same unit and just recently used it as is for making a Stilton and an Asiago. It performed well as is, but it had to be watched constantly and the manual aspect of temperature changes was difficult. Each are 27 days old, so a complete verdict is not yet possible, I will pass judgement in about a month.

First, when you heat and cook do you use the inner pan? If so you don't put liquid between the inner and out shell do you? The way I used it was to set then inner shell pan into the unit and I believe it is a slip fit with very little room between the wall.

I did experience a little scalding but not bad. I think this would be eliminated with your PID.

Second, can you give us a parts list of the PID and solid state relay that you used.

I'll admit my engineering ineptitude when I had wondered how the thermocouple worked; I presume it's used to measure the water jacket temp and given that it is an external probe, don't know how it drives the PID scheme; and yes, the actual components used would be very greatly appreciated. But the idea itself is already much appreciated.

Thermocouples are easy to understand. They are simply two wires made of two unlike metal alloys. Most of what we use in the food industry are called type K. One wire is made of chromel, the other wire is made of alumel. They are welded together at the end to form a bead.

When this bead is heated or cooled it was found that the two metals expand at different rates and as they do they also generate a small amount of voltage in direct proportion to temperature. We plug this wire into the PID and internal circuitry is used to convert the voltage to temperature. The rest of the PID is a computer that can use this data to control our cheese vat by turning on and off the heater at our set temps.

Logged

Cheese and Salumi: Cheese is Salumi from Milk, Salumi is Cheese from Meat. You bring the wine, I'll bring Cheese and Salumi!

Sailor, you kill me man. As I said on the post, the tape is just for running the test. It all goes into an elegant, solid, screwed-on stainless box fitted especially for it but it will take me a few more days. Paula Dean can only hope to get her hands on that!

steampwr8 - Yes, I intend on using the inner well to prevent scalding. I will try to put water in the mother well but don't know how much water I can realistically put there. I will also test it a couple of times until I know my deviation point so basically if I want 88F milk I will instruct the machine to go to 85.5F for example, expecting it to increase the heat in the next few minutes. Since milk is dense and hold temp very well and for a long time and we only need it to get to the right temp and then keep it there for an hour or two at the most, I trust that this will work very accurately.

I got a couple of PMs asking me for the shopping list with links, so here goes:

A note about wires: Go to your local Radio Shack or lighting/hardware store and make sure you get a couple of ft of high-temp cable. Normal appliance wire will melt and may even catch fire under the heating element. A typical high temp cable has braided insulation over a silicone or other heat-resistant insulation and looks like this:

Thermocouples are easy to understand. They are simply two wires made of two unlike metal alloys. Most of what we use in the food industry are called type K. One wire is made of chromel, the other wire is made of alumel. They are welded together at the end to form a bead.

When this bead is heated or cooled it was found that the two metals expand at different rates and as they do they also generate a small amount of voltage in direct proportion to temperature. We plug this wire into the PID and internal circuitry is used to convert the voltage to temperature. The rest of the PID is a computer that can use this data to control our cheese vat by turning on and off the heater at our set temps.

Thanks Steam. I should clarify I know what a thermocouple is - e.g., in my own experience, there are even home versions of CCVs for fermentation, with glycol jacketing and PID control - though I gained some proficiency with TIG welding and built my own SS, 1/2 bbl brewing system, never got to the point where I would venture the Unitank with glycol coolant, but understood the process; but just, as I say, unclear as to where the probe goes in this setup. (I think, something analogous to your question on using the inner/outer shell, and using/not using a water bath...I'm just confused as to literally where the sensor is placed).

The sensor would be either in the jacketing (water) bath, or milk itself, in order to send the (differential, given the setpoint) signal, yes? And if I understood correctly, iratherfly didn't want it in the milk (one more sanitization issue, milk stone, and obstructing cutting and stirring, as he mentions); so imagine it must be in the water jacket.

As I've never used a turkey roaster - maybe I'm just missing what it is? Is it not something like a soup warmer, with an outer shell - into which you can put water, for instance, which is temperature controlled - and an inner shell, the "double boiler" effect? And it's this inner shell which is either used to contain the milk (cheese vat) or water (sous vide)?

I will try to put water in the mother well but don't know how much water I can realistically put there.

Hey iratherfly,

Fine post !

I'm using a Hamilton Beach 18 qt and I find 10 cups of water in the main tank (shell) work for me with a four gallon load.

Another benefit of using the roaster design is for sterilizing equipment prior to a cheese make. I place all my stuff in the vat along with 2 cups water -- set it on the stove and heat to a solid steam for 15 min. leave the lid on till morning and I'm ready to go.

Buck 47 - you make a great point and thanks for the tip. Thanks for giving me a clue about how much water to try out. Are you using it to heat your milk now? At what temp do you turn it off if you for example, want a 90F milk and have 4 gallons in?

Determined, have you cooked sous vide before? The first stage in sous vide cooking is pasteurization. There are charts all over the internet that show you how long you need to keep each type of food in sous vide before it is fully safe. (these are minimum times. After these times you can keep most foods for hours in the machine). The second part of cooking is the breaking down of proteins and fats which tenderizes the food - actual cooking. A typical steak or lamb chop can be done in sous vide in 45 minute but for safety we give it 2 hours - by that time nothing had survived. Since the target temp is fixed and this is indeed anaerobic (vacuum), there is no overcooking, loss of moisture or oxidation. The steak will still be warm and perfect medium 8 hours later.

140F is the inner temperature of a perfect steak and a prime effective yet gentle pasteurization temp. Since the cooking time is well beyond the pasteurization time, everything is well pasteurized by the time you are done. In fact, you couldn't get such results cooking steak on a pan or grill even if you wanted to. Grilling meat the entire 9 minutes requires to pasteurize it will make it quite far from enjoyable medium. Proper sous vide is therefore actually safer.

Pathogens, like people are sluggish when cold, happiest at lukewarm temperature, and die in high heat rather quickly... According to the FDA getting rid of E.Coli and Salmonella in foods requires:86 min at 130F27 min at 135F9 min at 140F3 min at 145F52 sec at 150F5 sec at 160F1.6 sec at 165F

Even if you like it rare at 130F, after 2 hours and still perfect rare - it will be safer than any steak you've ever had. In spite of that, it is still recommended that if food is not consumed immediately it should be rabidly chilled and consumed within 3 days. The rapid chilling is done to shorten the time in which the food is at the "danger zone" temperature range, where bacteria loves to breed. You go from hot and dead to cold and sluggish without spending too much time at the happy and breeding zone.